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  <p>Categories can be used to throttle multiple projects.</p>
  <p>Categories can be optionally configured with pairs of throttled Jenkins node labels.<br>
     Pairs can make each maximum applicable to nodes with matching labels only.<br>
     That is achieved by adding such Maximum Per Labeled Node pair(s) to any category.<br>
     Category's Maximum Concurrent Builds Per Node is superseded by matching-pair's maximum.</p>
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